The embodiments herein relate generally to subterranean formation operations and, more particularly, to treatment fluids used in removing acid-soluble materials in subterranean formations.
Subterranean formations (e.g., hydrocarbon producing wells) are often stimulated by hydraulic fracturing treatments. In hydraulic fracturing treatments, a treatment fluid is pumped into a portion of a subterranean formation at a rate and pressure such that the subterranean formation breaks down and one or more fractures are formed. Typically, particulate solids are then deposited in the fractures. These particulate solids (“proppant particulates” or “proppant”) serve to prevent the fractures from fully closing once the hydraulic pressure is removed by forming a proppant pack. As used herein, the term “proppant pack” refers to a collection of proppant particulates in a fracture. By keeping the fracture from fully closing, the proppant particulates aid in forming conductive paths through which fluids may flow.
Subterranean formations may additionally be stimulated by acid treatments (“acidizing”). Acidizing involves introducing an acidic fluid into the formation to dissolve acid-soluble materials that may clog or constrict formation channels, such as the conductive paths formed between proppant particulates in a proppant pack. Acidic fluids may remove or reduce gas hydrates, among other materials, thus allowing produced fluids from the formation to flow more readily or easily through the formation and into a wellbore for production. Acidizing may also facilitate the flow of injected treatment fluids from the wellbore into the formation, when it is desired. In some instances, hydraulic fracturing may be performed using an acidic treatment fluid (“acid fracturing”).
Stimulation operations, and other subterranean formation operations, are designed to maximize production of fluids therefrom. Accordingly, creation of conductive channels in a formation at locations both in the near-wellbore region and far-field regions may be beneficial to increase fluid production. As used herein, the term “near-wellbore region,” or simply “near-wellbore,” refers to an annular volume of a subterranean formation penetrated by wellbore from the outer diameter of the wellbore extending radially inward from the wellbore and into the formation a distance of no greater than about 9 meters (30 feet). As used herein, the term “far-field region,” or simply “far-field” refers to an annular volume of a subterranean formation penetrated by wellbore from the outer diameter of the wellbore extending radially inward beyond the near-wellbore region. Both the near-wellbore region and the far-field region may further be defined along a length of a fracture when formed or existing in a subterranean formation, without departing from the scope of the present disclosure. In some instances, acid fluids may become spent (i.e., weakened or exhausted such that it is no longer fully effective, if at all) prior to reaching the far-field region, thus failing to fully realize the conductivity potential of a stimulation treatment job.